
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* 必须是p标签,而且添加了box类 */
     p.box {
        color: red;
    }
  </style>
</head>
<body>
<!-- 找到第一个p,带box类的, 设置文字颜色是红色 -->
<p class="box box1" id="dilireba">这是p标签:box</p>
<p class="box">这是p标签:box</p>
<p>pppppp</p>
<div class="box">这是div标签:box</div>
</body>
</html>